Because vehicles that use fossil fuels have serious effects on the generation of environmental pollution such as air pollution, electric vehicles or hybrid vehicles that generate almost no pollution have recently been developed and used. Electric vehicles or hybrid vehicles are configured to use the electric energy output from a battery installed therein to run. Also, a battery that is a power source for these vehicles is used with a plurality of secondary battery cells configured in one pack. Accordingly, the performance of a battery used in an electric vehicle or a hybrid vehicle is directly related to the performance of the vehicle, and a BMS (Battery Management System) for efficiently controlling the performance of the battery is required.
A battery management system performs the functions of: estimating a cell voltage, an overall battery voltage and current, and the like so as to efficiently manage the charging and discharging of cells; estimating an SOC (State of Charge) of cells, by calculation; and controlling the SOC. The estimating of the SOC may be performed by detecting the voltage, current, temperature, etc. of the cells, and the estimated SOC is controlled to more effectively control the power consumption of the battery.
The SOH (State of Health) of a battery is reduced according to an increase in the number of charge and discharge cycles thereof. Therefore, the number of charge and discharge cycles becomes a measure by which the SOH of the battery is estimated. Therefore, there is a need for a battery management system to manage information on the charge and discharge cycles of a battery and relay the information to a user in order to estimate the SOH of the battery.
A method that is used for managing information on the charge and discharge cycles of a battery according to the related art is one that simply performs counting when a certain value of the SOC or a certain value of an OCV (Open Circuit Voltage) is exceeded. However, with a method that performs counting only when a certain value is exceeded, it is difficult to obtain an accurate pattern of use for the charge and discharge cycles of a battery. Moreover, because an accurate pattern of use for the battery cannot be obtained, the estimation of the SOC of the battery, the maintenance of the battery, and the reliability in use of the battery all suffer.